Method of sewing textile webs together



Aug. 22, 1967 H. H. KUHN METHOD OF SEWING TEXTILE WEBS TOGETHER Filed Jan. 24. 1965 iexiiie web having a transverse butt seam, free from raised poriions,formed by hot pressing the sewing ihrecid formed of two fibrous components of lens? one of which is thermoplastic FIG. "2-

IN VEN TOR.

ATTORNEY United States Patent 3,337,381 METHGD 0F SEWING TEXTILE WEBS TOGETHER Hans H. Kuhn, Epartanburg, S.C., assignor to Deering Milliken Research Corporation, Spartanburg, S.C., a

corporation of Delaware Filed Jan. 24, 1963, Ser. No. 253,605 12 Clainis. (Cl. 156-93) ment. For example, in forming wool fabrics, the fabric is often sheared with a sharp blade to produce the desired surface on the fabric and when employing conventional procedures, a transverse seam interferes with this shearing operation. By conventional procedures, l00-yard lengths of wool fabric are sewn together to form transverse butt seams. When these seams approach the shearing blade, it is necessary to raise the blade momentarily to prevent the blade from cutting the threads in the seam and permitting the lengths of fabric to separate. Because of the speed at which the fabric travels in the shearing operation, as much as a quarter of a yard or more of the fabric is not sheared at the area of the seam and thus is waste fabric. Such a loss of fabric constitutes a considerable expense to the mill over a period of time.

Also, in the laminating and coating trade, where textile webs are subjected to high pressure calendering operations, a transverse seam having raised threads presents serious problems. If such a seam is present in the web, the pressure on the calender or laminating rolls ordinarily must be released momentarily and up to several yards of fabric are thus not properly calendered or laminated, because of the speed of laminating and calendering operations. Even if the seam is not raised sufficiently to require releasing the pressure from the pressure rolls, any raised portions at the seam will produce a visible defect in the surface of the coated fabric and thus produce a second, which must be sold at a lower price. Consequently, laminators and coaters sometimes refuse to purchase short lengths of fabric joined by a conventional transverse seam.

It is therefore an object of this invention to provide a method of joining together ends of textile webs so as to provide a seam substantially free from raised portions.

It is another object to provide a method of jomlng the ends of textile webs together so as to provide a seam which does not interfere with subsequent mechanical and/or chemical treatments of the textile web.

It is still another object to provide lengths of fabric having novel seams therein.

Other objects will be apparent to those skilled in the art to which this invention pertains.

According to this invention, lengths of textile webs are joined together by sewing to form a transverse butt seam with thread consisting essentially of from 20% to 70% of a thermoplastic first fibrous component which flows when heated and from 80% to 30% of a second fibrous component which neither flows nor substantially degrades when heated to the flow temperature of the first fibrous component. The seam is then heated under pressure so that the first component flows into the web and the second component is pressed tightly into the face of the web, thereby causing the exposed portions of the thread to be firmly and adhesively bonded to the face of the web. The heat and pressure are then removed, thus producing a seam substantially free from portions raised above the faces of the web.

The advantages of this novel process will be immediately apparent to those skilled in the art. This process now permits joining of the ends of textile webs by conventional sewing procedures and only a heating unit to which pressure can be applied is required to produce the desirable flat seam. It was surprising to find that as little as 20%, calculated on the weight of the thread, of the first fibrous component is necessary to achieve the desired results. It will be apparent that the exact minimum amount which can be employed in any particular situation will depend upon the adhesiveness of the selected first fibrous component to the selected web. The use of such small amounts substantially eliminates the possibility of any build-up of the thermoplastic material in the heating apparatus used to produce the bonded seam or in any subsequent operation in which the seamed web is brought in contact with a heated surface. This is particularly important in the wool industry where the wool is subject to decating or rotary press operations where any significant amounts of thermoplastic material on the web would be most undesirable. Also, the bonding of the seam can be completed in a very short time, which is especially desirable in such an operation.

This invention is illustrated in the acompanying drawings in which FIG. 1 is a schematic view of a portion of a textile web 1 having a transverse butt seam 2 therein formed with sewing thread 3 following this invention, and

FIG. 2 is a highly enlarged schematic cross-sectional view along line IIII of FIG. 1 of a woven fabric containing a transverse butt seam of the type shown in FIG. 1.

As shown in FIG. 2, the woven fabric 1, formed in the conventional manner from a multiplicity of warp ends 4 and filling ends 5 is butt seamed with a bicomponent sewing thread 6 containing a first fibrous component 7 and a second fibrous thermoplastic component 8 which as a result of the hot pressing given the seam, has flowed into the fabric and thus bonds the thread 6 tightly to the faces of the fabric 1. As FIG. 2 shows, the exposed portions of the sewing thread 6 have been pressed tightly into the face of the fabric by pressure which flattens the fabric threads 4a and 5a in the seam area as well as the exposed portions of the sewing thread so that the seam area is at the same height as or even below the level of the faces of the fabric.

Textile webs which can be seamed. according to the process of this invention include the woven, knitted and nonwoven fabrics. These fabrics can be formed of natur-al cellulosic materials, e.g., cotton, synthetic cellulosic material, e.g., unmodified and Polynosic rayons, and wool. Ordinarily, the process will be directed to fabrics con sisting entirely of nonthermoplastic materials. However, with the proper selection of the thermoplastic component in the sewing thread used in the process of this invention, the fabrics can consist partially or wholly of the synthetic thermoplastic materials, e.g., ethylene glycol terephthalate polyesters, the nylons, and the polyacrylics. The preferred webs employed in the process of this invention are the woven cotton, rayon and wool fabrics, particularly the latter where the savings in fabric by following the present process is highly significant.

The sewing thread used in the process of this invention contains from 20% to 70% of a thermoplastic first fibrous component and from to 30% of a second fibrous component, both as defined hereinafter, preferably at least 30% of each and more preferably between about 40% and 60% each. A 50:50 by weight mixture is very satisfactory. While the sewing thread will usually consist entirely of these two essential components, it can also include other materials, e.g., lubricants, waxes, softeners,

sizing materials, etc. As with all sewing threads, the thread should be formed of such materials and so constructed as to have sufiicient strength to withstand the sewing tensions and also so as to have substantial residual strength after the thermoplastic component has flowed in the heating operation so that the seam will not part when the textile web is subjected to the conventional processing tensions. The thermoplastic first fibrous component and the second fibrous component can be in the form of separate ends of a plied thread or blended together in the same end or ends. The blended form is preferred as it produces a significantly superior seam compared to the corresponding seam sewn with thread in which the two essential components are in separate ends of a plied thread. Either essential component can be in continuous filament or multifilament form and the other component in spun staple form or they both can be in filament, multifilament or in staple form.

The term fibrous means that the material is in continuous filament or staple form and has the properties of a textile fiber, as opposed to films or coatings.

The thermoplastic first fibrous component of the abovedescribed sewing thread is one having a Vicat flow temperature (A.S.T.M. D56959, procedure A) between about 100 and 225 C., which is below the temperature at which the web on which the seam is to be formed substantially degrades when heated for a short period, i.e., about one minute or less. Such materials include the fibrous forms of polypropylene, polyethylene, preferably high density polyethylene, polyvinyl alcohol, polyvinyl acetate, cellulose acetate and other thermoplastic deriva tives of cellulose, polyvinyl butyrates, the lower melting nylons, and other fiber-forming and polymeric materials, i.e., those polymers which can be spun and oriented into a fibrous form which can be formed into yarn. To improve flexibility, the conventional softeners and plasticizers can be incorporated in such thermoplastic materials. Thermoplastic fibrous materials which become thermosetting upon heating can also be used, e.g., the aminoplasts and the phenoplasts. Such materials are suitably employed where the textile web is subsequently subjected to a heating operation which would adversely affect a seam bonded with a nonthermosetting material. However, in practice it has been found that surprisingly the web containing the seam can be subjected to an operation such as a decating or a rotary press operation which heats the fabric at least momentarily to temperatures above the flow temperature of the thermoplastic component without adversely affecting the resultant seam or the equipment. The selected thermoplastic material should provide a relatively tack-free condition at room temperature to the thread, at least after the application of suiable anti-tack materials to the thread, so that the yarn can 'be sewn using conventional techniques. Of the thermoplastic first fibrous component employed, polypropylene gives outstanding results and is thus preferred. This is surprising in view of the fact that polypropylene does not have good adhesive properties generally.

The second fibrous component can be any fibrous material in the staple, filament or multifilament form which is conventionally employed in the textile industry to form yarns or threads and which neither flows nor is substantially degraded when heated at a temperature and for a time sulficient to cause the first fibrous component to flow. As the seam area is preferably heated to a temperature at least 25 C. above the flow temperature of the first fibrous component in forming the seam, the second fibrous component preferably does not flow or degrade at that temperature also. Preferably, the second fibrous component is nonthermoplastic, e.g., cotton, rayon or wool, but with proper selection of materials in the manner described above, nylons, ethylene glycol terephthalic polyesters, acrylics and other relatively high melting thermoplastic materials can be used. The second fibrous component should be a high strength material, i.e., one of il sufficient strength to form a useful sewing thread by itself. For various reasons, cotton is preferred as the second fibrous component.

As stated above, the two essential ingredients of the sewing thread can be intimately blended into one or more ends or they can be separate ends plied together. It has been found, however, that better adhesion is often obtained using the same materials if the two components are intimately blended together. Such a condition provides a superior sewing thread as well as a superior resultant seam.

The standard sewing thread construction with respect to plies, count or weight, and lNlSt per inch can be employed. Usually from 2-4 ends of ends with substantial twist in each end and plying twist is employed.

Because both components are fibrous, the sewing thread behaves normally in the sewing step and the thermoplastic component flows freely and readily around the second fibrous component and into the faces of the textile Web, thus providing superior adhesion.

In the sewing step the ends of the textile web are sewn together to form a butt, i.e., nonoverlapping, seam and the usual industrial railroad or other type sewing equipment can be used for this procedure or the sewing can be conducted by hand.

The textile web at the seam area is then subjected to substantial pressure, i.e., at least 10 pounds per square inch, preferably 25200 and more preferably 1OO pounds per square inch, so as to press the exposed portions of the sewing thread firmly into the face of the fabric. The amount of pressure required to do this will depend upon the yieldability of the web and the diameter of the sewing thread. Simple experimentation can readily determine the pressure required. Excessive pressures which cause destruc tive crushing of the fabric should be avoided. Only that pressure which presses the exposed portions of the sewing thread tightly into the plane of the faces of the web is required.

The fabric is then heated at the seam area while under the pressure described above to at least the flow temperature of the thermoplastic first fibrous component. Generally it is preferred to heat the seam to at least 25 C. above the flow temperature of the thermoplastic first fibrous component. However, the temperature to which the textile web is heated at the seam area should be below the temperatures which would cause substantial degradation of the web or of the fibrous supporting component, i.e., degradation sufiicient to weaken the fabric or the thread so that the web ends will part under conventional tensions applied in subsequent processing. As the preferred thermoplastic first fibrous components have a flow temperature between about and 200 C., more preferably about to 200 C., the web at the seam area will ordinarily be heated to a temperature between about 150 and 225 C. If the second fibrous component is also thermoplastic, e.g., nylon or Dacron, somewhat greater care must be exercised to ensure that the web is not heated at the seam area to a temperature which causes substantial loss in strength of the second fibrous component. However, if the temperature to which the web is heated does not substantially exceed 225 0, sufficient strength in the thread will be retained to hold the seam together in subsquent operations.

If the means for applying pressure to the seam is a heated platen, which is the preferred apparatus for performing the process of this invention, the heating of and applying pressure to the web will occur substantially simultaneously. Apparatus of the type shown in U.S. Patent No. 3,000,434 is suitable for this purpose.

The seam area is heated at the selected temperature for a time sufficient to cause the thermoplastic component to flow through the yarn and into the textile web. This generally requires less than one minute and usually less than 45 seconds, e.g., 2 to 35 seconds, depending, in part, upon the temperature employed, the flow temperature of the thermoplastic component and the efiiciency of the heating system employed, e.g., diathermic vs. conductive heating. All that is required is that the flow temperature of the thermoplastic component be reached.

The seam is then permitted to cool below the softening temperature of the thermoplastic component. This causes the sewing thread to adhere tightly to the face of the fabric by a diffusion of the thermoplastic component through the sewing thread and into the fabric. The pressure is, of course, also removed either before, at the same time as or after the heating means is removed from the seam.

The following examples are illustrative of the processes and products of this invention but are not to be construed as limiting. Unless otherwise indicated proportions and percentages are on a weight basis.

Example I Sew together two ends of a conventional all-wool worsted fabric using a conventional railroad sewing machine to form a narrow butt seam, using as sewing thread a 50:50 mixture of 1.5 x 1.5 polypropylene staple and cotton staple, spun together into 40s cotton count Z. t.p.i. singles yarn and then plied into a 4 ply S. t.p.i. sewing thread. Using a platen about 1.5 inches wide and about 72 inches long, heated to about 200 C.i4 C., press the sewing thread tightly into the face of the fabric with about 70 lbs/sq. in. pressure. Apply the heat and pressure for about 30 seconds. Raise the platen so as to permit the seam to cool. The resulting seam presents no portions of the sewing thread raised above the face of the fabric. Consequently, the fabric can be passed through a shearing operation without raising the blade at the seam area or cutting the sewing threads to any significant extent. The adhesion of the threads on the face of the fabric is excellent so that the fabric can pass through a heated rotary press without releasing the threads from the face of the fabric or causing the fabric to stick to the rotary press.

Example II Follow the procedure of Example I, using a sewing thread formed of a 30:70 mixture of 1.5 x 1.5 polypropylene staple and cotton staple, spun into 15s cotton count 16.5 Z. t.p.i. singles yarn and then plied into a 2 ply 10 S. t.p.i. sewing thread. Press for 30 to 45 seconds. Adhesion is good but somewhat less than when using the 50:50 mixture. No raised portions of the sewing thread will be apparent on either face of the fabric.

Any, some, or all of the following variations can be incorporated into the procedures of Examples I and II:

(a) The proportion of polypropylene to cotton can be varied from :80 to 70:30.

(h) The platen temperature can be varied from 190 to 225 C. and the heating time varied, inversely to the change in temperature, from 10 to 120 seconds.

(c) The pressure can be varied from to 200 lbs/sq. in.

(d) The substrate fabric can be ethylene glycol terephthalic acid polyester, polyacrylic, nylon, cotton, rayon, blends of any of these with wool, or blends of any two or more of these.

(e) The polypropylene can be replaced by cellulose triacetate, polyvinyl acetate, polyvinyl chloride, high density polyethylene or polyurethane, in staple, monofilament or multifilament form.

(f) The cotton can be replaced by rayon, nylon, ethylene glycol terephthalic acid polyester, polyacrylic in staple, monofilament or multifilament form.

Example Ill Follow the procedure of Example I using a 3 ply sewing thread formed of two ends of 40s singles cotton and one end of 210/35 multifilament polypropylene plied together. The finished seam displays no portions raised above the face of the fabric and adhesion is excellent.

6 Example IV Follow the procedure of Example I using a sewing thread formed from one end of No. 30 cotton sewing thread (Signal Thread Co.) and one end of denier monofilament polypropylene. Heat under pressure for 45 seconds. As in Example I, adhesion of the thread to the fabric substrate is excellent and the thread is pressed well into the faces of the fabric.

Example V Follow the procedure of Example I using as sewing thread 25/2 plied yarn formed of a 50:50 mixture of viscose and cellulose acetate blended and spun together. Heat for .45 seconds. A rather stiff seam is formed, but there are no raised portions and adhesion is excellent.

Example VI Follow the procedure of Example V .but plasticize the sewing thread before use by padding with butyl phthalyl butyl glycolate plasticizer (Monsanto Sanitizer B-16). A softer, more pliable seam than that obtained using the sewing thread described in Example V is produced. Adhesion remains excellent.

This procedure using the above-described sewing thread is particularly suited for joining together ends of cotton fabric intended to be plastic coated or laminated.

Example VII Follow the procedure of Example ll, using 2 ends of 210/35 Hercules multifilament polypropylene and 2 ends of 200/20 Du Pont multifilament nylon plied 17 t.p.i. Press at 205 C. for 30 seconds. A flexible, strong seam is produced adhering tightly to the face of the fabric and presenting no portions raised substantially above the faces of the fabric.

Example VIII Follow the procedure of Example VII, but substituting 200/44 viscose bright rayon for the nylon. Substantially the same results are obtained.

What is claimed is:

1. A method of joining together the ends of lengths of textile webs so as to provide a seam substantially free from raised portions which comprises the steps of (1) butting the ends of lengths of textile webs;

(2) sewing the ends of the webs together to form a butt seam with a bicomponent sewing thread comprising (a) from 20% to 70% of a thermoplastic first fibrous component having a flow temperature, between about and 225 C., which is below the temperature at which the web substantially degrades when heated for about one minute, and

(b) from 80% to 30% of a second fibrous component which neither flows nor substantially degrades when heated for up to about one minute to the flow temperature of the thermoplastic first fibrous component;

(3) applying sufiicient pressure to the seam to press the raised portions of the thread in the seam tightly into the face of the web;

(4) applying suflicient heat, while the seam is under pressure so as to heat the web at the seam position to at least the flow temperature of the thermoplastic first fibrous component but below the degradation temperatures of both the web and the second fibrous component, for a period of time sufiic-ient to permit the thermoplastic first fibrous component to flow; and

(5) cooling the seam and releasing the pressure therefrom.

2. A method according to claim 1 wherein the second fibrous component is a nonthermoplastic cellulosic material.

3. A method according to claim 1 wherein the first fibrous component is polypropylene.

4. A method according to claim 1 wherein the first fibrous component is plasticized cellulose acetate.

5. A method according to claim 1 wherein the first fibr'ous component and the second fibrous component are both in staple form blended and spun together.

6. A method according to claim 1 wherein the web is woven fabric.

7. A method according to claim 1 wherein the fabric comprises wool.

8. A method of joining together the ends of lengths of woven fabric comprising wool so as to permit the fabric to pass through a shearing operation without raising the shearing blades at the joined ends which comprises the steps of (1) butting the ends of lengths of woven fabric;

(2) sewing the ends of the fabric together to form a butt seam with a sewing thread comprising at least 30% each of (a) a thermoplastic first fibrous component having a flow temperature between about 125 and 200 (3.,

(b) a nonthermoplastic second fibrous component which does not substantially degrade when heated to a temperature at least 25 C. above the flow temperature of the thermoplastic first fibrous component for up to about one minute;

(3) applying sufi'lcient pressure to the seam to press the raised portions of the sewing thread in the seam tightly into the face of the fabric;

(4) applying sufficient heat, while the seam is under pressure, so as to heat the fabric at the seam portion to a temperature from at least 25 C. above the flow temperature of thermoplastic first fibrous con1po nent to 225 C., for a time sufiicient to permit the thermoplastic first fibrous component to flow; and (5) cooling the seam. 9. A method according to claim 8 wherein the thermoplastic first fibrous component is polypropylene.

10. A method according to claim 8 wherein the nonthermoplastic second fibrous component is a cellulosic.

11. A method according to claim 8 wherein the thermoplastic first fibrous component and the nonthermoplastic second fibrous component are both in staple form blended and spun from the thread.

12. A method according to claim 8 wherein the thermoplastic first fibrous component is polypropylene and the nonthermoplastic second fibrous component is cotton.

References Cited UNITED STATES PATENTS 2,252,999 8/1941 Wallach l6l150 X 2,483,405 10/1949 Francis 161--150 2,592,463 4/1952 Phillips l6l52 X 2,624,886 1/1953 Herman 16l--50 2,631,957 3/1953 Francis 156-178 X 2,668,296 2/1954 Welch 161-50 2,974,559 3/1961 Coggi 161-l76 X 2,994,631 8/1961 Ottinger 15693 3,001,905 9/1961 Morin 15693 3,234,061 2/1966 Gardner 156-93 FOREIGN PATENTS 514,934 7/1955 Canada.

EARL M. BERGERT, Primary Examiner.

H. F. EPSTEIN, Assistant Examiner. 

1. A METHOD OF JOINING TOGETHER THE ENDS OF LENGTHS OF TEXTILE WEBS SO AS TO PROVIDE A SEAM SUBSTANTIALLY FREE FROM RAISED PORTIONS WHICH COMPRISES THE STEPS OF (1) BUTTING THE ENDS OF LENGTHS OF TEXTILE WEBS; (2) SEWING THE ENDS OF THE WEBS TOGETHER TO FORM A BUTT SEAM WITH A BICOMPONENT SEWING THREAD COMPRISING (A) FROM 20% TO 70% OF A THERMOPLASTIC FIRST FIBROUS COMPONENT HAVING A FLOW TEMPERATURE, BETWEEN ABOUT 100* AND 225*C., WHICH IS BELOW THE TEMPERATURE AT WHICH THE WEB SUBSTANTIALLY DEGRADES WHEN HEATED FOR ABOUT ONE MINUTE, AND (B) FROM 80% TO 30% OF A SECOND FIBROUS COMPONENT WHICH NEITHER FLOWS NOR SUBSTANTIALLY DEGRADES WHEN HEATED FOR UP TO ABOUT ONE MINUTE TO THE FLOW TEMPERATUR OF THE THERMOPLASTIC FIRST FIBROUS COMPONENT; (3) APPLYING SUFFICIENT PRESSURE TO THE SEAM TO PRESS THE RAISED PORTIONS OF THE THREAD IN THE SEAM TIGHTLY INTO THE FACE OF THE WEB; (4) APPLYING SUFFICIENT HEAT, HWILE THE SEAM IS UNDER PRESSURE SO AS TO HEAT THE WEB AT THE SEAM POSITION TO AT LEAST THE FLOW TEMPERATURE OF THE THERMOPLASTIC FIRST FIBROUS COMPONENT BUT BELOW THE DEGRADATION TEMPERATURE OF BOTH THE WEB AND THE SECOND FIBROUS COMPONENT, FOR A PERIOD OF TIME SUFFICIENT TO PERMIT THE THERMOPLASTIC FIRST FIBROUS COMPONENT TO FLOW; AND (5) COOLING THE SEAM AND RELEASING THE PRESSURE THEREFROM. 